Organometallics
Article
mmol) in THF (100 mL) was cooled to 0 °C, and butylamine (10.9
mL, 110 mmol) was added dropwise. The solution was stirred at 0 °C
for 15 min and then warmed to room temperature and stirred for an
additional 12 h. Evaporation of the solvent in vacuo afforded the
1.0 mmol) and stirred at room temperature for 12 h. The color
changed to dark red-brown. The crude material obtained upon drying
the reaction mixture in vacuo was redissolved in toluene (5.0 mL) and
separated from KCl via centrifugation. The product was recrystallized
from toluene at −35 °C, yielding red crystals of 5 (0.31 g, 0.67 mmol,
67%). μeff = 3.63 μB. ESI-MS calcd (found): 420.1380 (420.2056).
Anal. Calcd (found) for C17H31Cl2CrN2O2: C, 49.04 (49.86); H, 7.02
(7.17); N, 6.73 (7.29).
Preparation of (PyrN)Cr(acac)2 (6). A solution of PyrN (0.23 g,
1.5 mmol) in THF (7.0 mL) was treated with KH (0.13 g, 3.3 mmol),
and the mixture was stirred at room temperature for 12 h. The
resulting golden yellow suspension was treated with Cr(acac)3 (0.52 g,
1.5 mmol) and stirred at room temperature for 12 h. The color
changed to dark red-brown, and the mixture was evaporated to
dryness. The crude material was further dried in vacuo, redissolved in
toluene (5.0 mL), and separated from K(acac) via centrifugation. The
product was recrystallized from toluene at −35 °C, yielding red
crystals of 6 suitable for X-ray diffraction (0.21 g, 0.5 mmol, 35%). μeff
= 3.62 μB. Anal. Calcd (found) for C19H28CrN2O4: C, 56.85 (55.95);
H, 7.28 (7.09); N, 6.98 (7.35).
Preparation of (PyrNPy)CrCl2(THF) (7). A solution of PyrNPy
(0.97 g, 4.0 mmol) in THF (20.0 mL) was treated with KH (0.18 g,
4.4 mmol), and the mixture was stirred at room temperature for 12 h.
The resulting dark red-brown solution was treated with CrCl3(THF)3
(1.5 g, 4.0 mmol) and stirred at room temperature for 12 h, while the
color changed to dark green. The material was dried in vacuo and the
residue redissolved in toluene (12.0 mL) and separated from KCl via
centrifugation. The product was recrystallized from toluene at −35 °C,
yielding small green crystals of 7 (0.87 g, 2.0 mmol, 50%). μeff = 3.83
μB. ESI-MS calcd (found): 367.1716 (367.2263). Anal. Calcd (found)
for C21H31Cl3CrN2OP: C, 52.30 (52.97); H, 6.24 (6.15); N, 9.63
(9.02).
Preparation of (PyrNPy)Cr(acac)2 (8). A solution of PyrNPy
(0.24 g, 1 mmol) in THF 8.0 mL) was treated with KH (0.04 g, 1.1
mmol), and the mixture was stirred at room temperature for 12 h. The
resulting dark red-brown solution was treated with Cr(acac)3 (0.35 g,
1.0 mmol) and stirred at room temperature for 12 h, while the color
changed to dark brown. The crude material was dried in vacuo,
redissolved in toluene (6.0 mL), and separated from K(acac) via
centrifugation. The product was recrystallized from toluene at −35 °C,
yielding small brown crystals of 8 (0.31 g, 0.63 mmol, 63%). μeff = 3.73
μB. ESI-MS calcd (found): 491.1877 (491.3080). Anal. Calcd (found)
for C21H31Cl3CrN2OP (found): C, 60.96 (60.50); H, 6.96 (6.76); N,
8.53 (7.91).
Polymerization Methods. The copolymerizations were per-
formed both in bulk and in solution with a [cyclohexene
oxide:catalyst:cocatalyst] ratio of [500:1:1], unless stated otherwise.
Bulk. A mixture of cyclohexene oxide (5.09 mmol) and catalyst
(10.19 μmol) and cocatalyst (10.19 μmol) was reacted in a 5 mL glass
sleeve equipped with a stirring bar and placed inside a bomb reactor
and pressurized with 50 bar of CO2. The reactor was placed in an oil
bath on a stirrer/heating plate. The polymerization was conducted at
80 °C, unless stated otherwise. All analyses were performed on crude
samples.
Solution. A 5 mL glass sleeve equipped with a stirring bar was
placed inside a bomb reactor and charged with a mixture of CHO
(5.095 mmol), catalyst (10.19 μmol), and cocatalyst (10.19 μmol) in
toluene (1 mL) and pressurized with 50 bar of CO2. The reactor was
placed in an oil bath and mounted on top of a stirrer/heating plate.
Polymerization was conducted at 80 °C, unless stated otherwise. All
analyses were performed on crude samples.
Analysis of Polymers. NMR spectra were recorded on a Varian
Mercury Vx (400 MHz) spectrometer at 25 °C in chloroform-d, and
1H NMR spectra were referenced internally using residual solvent
proton signals. For 1H NMR experiments, the spectral width was
6402.0 Hz, the acquisition time was 1.998 s, and the number of
recorded scans was equal to 64. SEC analyses were carried out using a
Waters 2695 separations module, a Model 2414 refractive index
detector (at 40 °C), and a Model 486 UV detector (at 254 nm) in
series. Injections were done by a Waters Model WISP 712
1
product as a dark red oil (14.9 g, 100 mmol, 100%). H NMR (400
MHz, CDCl3): δ 11.37 (s, 1H, N−H), 8.16 (s, 1H), 6.91 (s, 1H), 6.57
(d, J = 2.4 Hz, 1H), 6.29 (t, J = 3.0 Hz, 1H), 3.64 (t, J = 6.8, 2H), 1.68
(m, 2H), 1.44 (m, 2H), 0.98 (t, J = 7.4, 3H). 13C NMR (400 MHz,
CDCl3): δ 152.1, 130.3, 122.0, 114.2, 109.4, 60.5, 33.3, 20.3, 13.4.
Preparation of 1H-Pyrrol-2-ylmethylbutylamine (Pyr-N).53
A
solution of N-butyl-N-(1H-pyrrolemethylidene)amine (8.0 g, 53
mmol) in distilled methanol (80 mL) was cooled to 0 °C, and excess
NaBH4 (4.0 g, 105 mmol) was added slowly. Gas evolution was
observed. The resulting brown suspension was stirred at room
temperature overnight and then concentrated to 50 mL in vacuo. The
excess NaBH4 was quenched with 50 mL of water, and the aqueous
solution was extracted three times with diethyl ether (3 × 30 mL). The
combined Et2O fractions were dried over MgSO4 and filtered, and the
solvent was evaporated in vacuo, affording the product as a red-orange
oil (6.89 g, 45 mmol, 70%). 1H NMR (400 MHz, CDCl3): δ 10.04 (s,
1H N−H pyrrole), 6.76 (s, 1H), 6.21 (s, 1H), 6.15 (s, 1H), 3.86 (s,
2H), 2.74 (t, J = 7.2 Hz, 2H), 1.60 (m, 2H), 1.46 (m, 2H), 1.03 (t, J =
7.2, 3H). 13C NMR (400 MHz, CDCl3): δ 130.4, 117.5, 107.8, 106.4,
49.2, 46.7, 32.0, 20.5, 14.0.
Preparation of N-Butyl-N-(2-pyridylmethyl)-N-(1H-2-
pyrrolylmethyl)amine (Py-N-Pyr).53 A suspension of Na2CO3
(7.7 g, 4.0 mmol) in water (12 mL) was added to 100 mL of cooled
(0 °C) methanol. To the resulting suspension, was added picolyl
chloride hydrochloride (3.8 g, 23 mmol), and the mixture was stirred
at 0 °C for 2 h while a pink suspension was formed. Neat 1H-pyrrol-2-
ylmethylbutylamine (3.5 g, 23 mmol) was added to the pink
suspension, and stirring was continued at room temperature for 5
days. The color slowly changed from pink to pale orange. The
suspension was filtered and the filtrate collected and concentrated in
vacuo. The resulting solution was washed with chloroform (3 × 15
mL), and the chloroform fractions were combined and dried over
MgSO4. After filtration and solvent evaporation in vacuo, a yellow oil
was obtained and purified by column chromatography over silica-60H
1
with 10% MeOH/90% CHCl3 (1.73 g, 7.13 mmol, 31%). H NMR
(400 MHz, CDCl3): δ 9.82 (broad s, NH), 8.55 (d, J = 4 Hz, 1H),
7.66 (m, 1H), 7.42 (d, J = 8, 1H), 7.18 (m, 1H), 6.78 (m, 1H), 6.13
(m, 1H), 6.03 (s, 1H), 3.89 (s, 2H), 3.58 (s, 2H), 2.48 (t, J = 6.4, 2H),
1.53 (m, 2H), 1.30 (m, 2H), 0.88 (t, J = 7.2, 3H). 13C NMR (400
MHz, CDCl3): δ 159.4, 148.8, 136.7, 128.1, 124.1, 122.2, 117.3, 107.7,
107.6, 58.9, 54.0, 49.3, 29.4, 20.6, 14.1.
Preparation of (PyNZn(CH2CH3)Cr(CH2CH3)Cl2)2 (3). A solution
of 1 (0.27 g, 0.50 mmol) in toluene (5 mL) was cooled to −30 °C for
about 5 min, and then Zn(CH2CH3)2 was added dropwise (0.31 g, 2.5
mmol) and the resultant dark green solution was stirred at room
temperature for 20 min. The insoluble solid material was discarded by
centrifugation, and the resulting solution was cooled to −30 °C for 4
days. Blue block-shaped crystals of 3 were isolated and washed with
cold hexanes (3 × 2 mL) and dried (0.19 g, 0.26 mmol, 52%). μeff
=
3.88 μB. Anal. Calcd (found) for C22H38Cl4Cr2N4Zn2: C, 35.94
(36.69); H, 5.21 (4.22); N, 7.62 (7.06).
Preparation of (Pyr=N)2CrCl(THF) (4). A solution of Pyr=N
(0.15 g, 1 mmol) in THF (5.0 mL) was treated with KH (0.04 g, 1.1
mmol) and the mixture stirred at room temperature for 12 h. The
resulting pale red suspension was treated with CrCl3(THF)3 (0.19 g,
0.5 mmol) and stirred at room temperature for 12 h. The color
changed to dark red. The crude material was dried in vacuo,
redissolved in hexane (5.0 mL), and separated from KCl via
centrifugation. The product was recrystallized from hexane at −35
°C, yielding small red crystals of 4 suitable for X-ray analysis (0.18 g,
0.4 mmol, 53%). μeff = 3.78 μB. Anal. Calcd (found) for C27H37CrN6:
C, 64.91 (64.08); H, 7.87 (7.33); N, 16.82 (15.93).
Preparation of (PyrN)CrCl2(THF)2 (5). A solution of PyrN (0.15
g, 1 mmol) in THF (5.0 mL) was treated with KH (0.09 g, 2.2 mmol),
and the mixture was stirred at room temperature for 12 h. The
resulting peach-colored suspension was treated with Cr(acac)3 (0.35 g,
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dx.doi.org/10.1021/om5005644 | Organometallics 2014, 33, 4401−4409